Question

A doctor wants to estimate the mean HDL cholesterol of all​ 20- to​ 29-year-old females. How many subjects are needed to estimate the mean HDL cholesterol within

3

points with

99 %

confidence assuming

s= 10.8

based on earlier​ studies? Suppose the doctor would be content with

95 %

confidence. How does the decrease in confidence affect the sample size​ required?

Answer 1

for 99% CI:

for 99 % CI value of z=	2.576
standard deviation σ=	10.80
margin of error E =	3
required sample size n=(zσ/E)2                                         =	86.0

for 95% CI:

for 95 % CI value of z=	1.960
standard deviation σ=	10.80
margin of error E =	3
required sample size n=(zσ/E)2                                         =	50.0

for 95% CI ;   sample size​ requirement reduces,